1. Field of the Invention
This invention relates, generally, to needles used to implant radioactive seeds.
More particularly, it relates to a prostate seeding needle where a leading seed is housed in a bio-absorbable housing.
2. Description of the Prior Art
Radioactive seeds and spacers in a specific array are placed into a prostate in standard brachytherapy. The seeds and spacers are slidingly received within the lumen of a needle and the needle is inserted into the prostate. A stylet is introduced into the proximal end of the needle so that the leading end of the stylet abuts the trailing end of the last seed or spacer. The position of the stylet is maintained as the needle is retracted, thereby leaving the seeds and spacers in the prostate. The stylet is then removed along with the needle.
Bone wax is commonly used to plug the distal end of the needle to prevent the seeds and spacers from falling out of the needle during transport prior to use.
U.S. Pat. No. 6,569,077 to the present inventor discloses a seeding needle having a dimple formed near a distal end thereof. The dimple provides an interior protuberance that forms a barrier in the lumen. A flexible and resilient plug is placed at the distal end of a string of seeds and spacers. The flexible and resilient plug has a diameter greater than that of the string of seeds and spacers so that the dimple prevents unwanted proximal-to-distal travel of the plug and thus of the string behind it. When it is desired to deploy the seeds and spacers into a prostate, the seeding needle is introduced into the prostate to a predetermined position. A stylet positioned at the proximal end of the string is held in position while the seeding needle is retracted. The flexible and resilient plug is momentarily deformed as it squeezes past the restricting dimple. After the plug has squeezed past the protuberance, the plug and the string of seeds and spacers behind it are properly deployed as the seeding needle is fully withdrawn along with the stylet.
Thus, the protuberance formed by the dimple supplants the bone wax of the prior art. This makes the distance between the first seed and the distal end of the needle more uniform than was obtainable using only bone wax as a seed and spacer retention means.
It is desirable for the first seed to be as close as possible to the distal end of the needle, allowing precise placement of the first seed. The only drawback of the above-described wax-less system is that the first seed in the string is spaced from the distal end of the seeding needle by a distance equal to the length of the protuberance from the distal end of the seeding needle, plus the length of the plug itself. For example, if the retaining plug is 0.040–0.080 inches in length, the first seed is that distance behind the dimple. Accordingly, precision is lost as to exactly where the first seed is in relation to the distal tip of the seeding needle.
The distance variation caused by the use of bone wax is thus substantially reduced, but the plug itself also introduces a distance variation.
Thus there is a need for an improved system that does not rely upon bone wax or the flexible and resilient plug.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how such need could be fulfilled.